It’s rarely a good idea to shy away from unfamiliar terms when we’re trying to learn something more thoroughly. The dragons that hide on the path have one trick they play over and over: they whisper (if dragons can ever be said to whisper) that all those technical terms are useless and that we’re better served to just do it and call it done. Ironically, that can end up being the long way home. And if there’s one subject with its fair share of terminology, it’s grammar.
Writing a good sentence or paragraph involves what is called cohesion. Most of us write most of the time to explain or describe something, and what we’re writing about is usually not simple: someone did this after that because of this so that that. The frame of mind your reader brings to your writing (like the mind you’re in right now reading this) is the rational, the one that sectionalizes experience, divides it up with nouns and verbs, makes a little model of what it wants to say, and gives that design, that composition, to the reader to see, to observe, or even to behold. All the many parts of that composition must cohere, must cling together in some organized manner so that together they represent meaning.
Now it’s to this end of cohesion that what is called a relative adverb works. Take this grammatically complex sentence: Let’s put these new sweaters here by the door, where customers can see them when they walk in. The comma in this sentence marks the division between two clauses, the first an independent clause that’s issuing a command (let us), and the other a subordinate clause of some sort—subordinate because it relies on the first clause for its own complete sense: merely to say where customers can see them when they walk in will leave everyone, including the customers, confused. The two clauses are connected, or related, by the adverb where, and so that word functions as what is termed, appropriately enough, a relative adverb (sometimes also called, for the same reason, a conjunctive adverb). This special term is needed to differentiate the construction from a simple adverb of place, for the clause where customers can see them intends to give the reason why we would put them here by the door. The relative adverb where is crossing the border between the two clauses and bringing an idea in each together.
If all this looks suspiciously similar to how a relative pronoun works, that would not be a coincidence. If we wanted to revise the sentence in order to write around the relative adverb, we might compose this: Let’s put these new sweaters here by the door, at the place in which customers can see them when they walk in. Not a better revision, but one that lays bare the mechanism inside the relative adverb: where in the original version means in which. The word which is a relative pronoun (the object of the preposition in), and as a relative pronoun, its antecedent is the noun place. The noun place, in turn, is the object of the preposition at, and so in this lesser revision, it has taken five words to say what the one-word relative adverb where could signify more simply and more elegantly. And writers, like mathematicians, hold simplicity and elegance in high regard.
Some (not all) of the other relative adverbs are when (she stood up when everyone began to applaud); while (the doctor listened while the patient breathed deeply); and until (the board was unaware of the problem until they read the letter from a resident). Each of these is likewise abbreviating a longer locution involving a relative pronoun (when, for example, means at the time in which). Being aware of the compositional device of the relative adverb can help us stay ready and able to employ a smart devise to keep our prose crisp. Alerting us is what a technical terminology is all about, so that we can discover choices that might otherwise remain concealed by those jealous dragons on the path.